硅酸盐矿物-水界面产生活性氧及其氧化Ce(III)的机制

在蓝细菌进化产氧光合作用之前，太古代地表在极端缺氧的大气下局部出现氧化风化，这些氧化事件主要由非生物氧化剂导致。我们前期研究发现，石英-水界面反应可产生过氧化氢、羟基自由基等活性氧组分（ROS），并形成太古代局部氧化环境，为产氧光合作用进化提供H2O2。我们关注到多种硅酸盐矿物经机械磨蚀后均可产生ROS，这可能对太古代地表氧化有重要贡献。然而，不同矿物产氧能力存在差异及其控制因素尚不明确，制约了人们对ROS在早期氧化事件中所扮演重要角色的认识。本申请拟在模拟太古代极端缺氧的大气条件下，采用自由基捕获实验技术，研究不同结构的硅酸盐矿物产生ROS的能力及其控制因素，并以Ce异常作为示踪氧化还原环境变化的指标，开展ROS氧化Ce(III)的实验，检验ROS导致太古代地表氧化风化的可行性。本研究有潜力提供一种具有重要地质意义的非生物产氧途径，同时提供一种正向演绎早期地球演化的实验矿物学研究方法。

Prior to the innovation of oxygenic photosynthesis by cyanobacteria, local oxidative weathering occurred on the Archean terrestrial surfaces beneath the anoxic atmosphere, which were mainly triggered by abiotic oxidants. Our previous study found that, reactive oxidizing species (ROS, e. g., H2O2 and •OH) could be generated at quartz-water interface, which could have created local oxidized environments in the Archean and provided H2O2 for the oxygen-requiring evolution of oxygenic photosynthesis. We notice that various silicates that experienced mechanic abrasions can react with water and produce ROS, which might have contributed to the oxidation of the Archean terrestrial surface. However, the ROS production of various silicates and their constraint by structural factors are not clear, which limits the understanding in the role of ROS in early oxidative weathering. This application intends to investigate the ROS production at various silicate-water interfaces and their control mechanism by using the free radical-capturing experiment techniques. The Ce anomaly is taken as the proxy to trace changes in redox conditions, and ROS-oxidizing Ce(III) experiments will be conducted to test the feasibility of triggering the Archaean oxidative weathering by ROS. This research has the potential to provide a geologically significant abiotic oxygen-producing pathway, and an experimental mineralogy method for deducing the evolution of the early Earth.